diff --git a/core/utils/tests_utils.py b/core/utils/tests_utils.py
new file mode 100644
index 0000000..8d6e2f7
--- /dev/null
+++ b/core/utils/tests_utils.py
@@ -0,0 +1,88 @@
+from unittest import TestCase
+from unittest.mock import MagicMock, patch
+
+from langcodes import Language
+
+from core.utils.utils import _get_user, language_iso
+
+
+class LanguageIsoTests(TestCase):
+    """Tests for the ``language_iso`` helper."""
+
+    def test_normalises_pt_br(self):
+        self.assertEqual(language_iso("pt-BR"), "pt")
+
+    def test_normalises_en_us(self):
+        self.assertEqual(language_iso("en-US"), "en")
+
+    def test_normalises_es_419(self):
+        self.assertEqual(language_iso("es-419"), "es")
+
+    def test_simple_code_unchanged(self):
+        self.assertEqual(language_iso("fr"), "fr")
+
+    def test_empty_string_returns_empty(self):
+        self.assertEqual(language_iso(""), "")
+
+    def test_none_returns_empty(self):
+        self.assertEqual(language_iso(None), "")
+
+    def test_invalid_code_returns_empty(self):
+        self.assertEqual(language_iso("zzzzzz"), "")
+
+
+class GetUserTests(TestCase):
+    """Tests for the ``_get_user`` helper."""
+
+    @patch("core.utils.utils.get_user_model")
+    def test_resolves_by_request_user_id(self, mock_get_user_model):
+        mock_user_model = MagicMock()
+        mock_get_user_model.return_value = mock_user_model
+        request = MagicMock()
+        request.user_id = 42
+        sentinel = object()
+        mock_user_model.objects.get.return_value = sentinel
+
+        result = _get_user(request)
+
+        mock_user_model.objects.get.assert_called_once_with(pk=42)
+        self.assertIs(result, sentinel)
+
+    @patch("core.utils.utils.get_user_model")
+    def test_falls_back_to_user_id(self, mock_get_user_model):
+        mock_user_model = MagicMock()
+        mock_get_user_model.return_value = mock_user_model
+        request = MagicMock(spec=[])  # no user_id attribute
+        sentinel = object()
+        mock_user_model.objects.get.return_value = sentinel
+
+        result = _get_user(request, user_id=7)
+
+        mock_user_model.objects.get.assert_called_once_with(pk=7)
+        self.assertIs(result, sentinel)
+
+    @patch("core.utils.utils.get_user_model")
+    def test_falls_back_to_username(self, mock_get_user_model):
+        mock_user_model = MagicMock()
+        mock_get_user_model.return_value = mock_user_model
+        request = MagicMock(spec=[])  # no user_id attribute
+        sentinel = object()
+        mock_user_model.objects.get.return_value = sentinel
+
+        result = _get_user(request, username="alice")
+
+        mock_user_model.objects.get.assert_called_once_with(username="alice")
+        self.assertIs(result, sentinel)
+
+    @patch("core.utils.utils.get_user_model")
+    def test_user_id_preferred_over_username(self, mock_get_user_model):
+        mock_user_model = MagicMock()
+        mock_get_user_model.return_value = mock_user_model
+        request = MagicMock(spec=[])  # no user_id attribute
+        sentinel = object()
+        mock_user_model.objects.get.return_value = sentinel
+
+        result = _get_user(request, username="alice", user_id=7)
+
+        mock_user_model.objects.get.assert_called_once_with(pk=7)
+        self.assertIs(result, sentinel)
diff --git a/core/utils/utils.py b/core/utils/utils.py
new file mode 100644
index 0000000..da8b463
--- /dev/null
+++ b/core/utils/utils.py
@@ -0,0 +1,56 @@
+import logging
+
+from django.contrib.auth import get_user_model
+
+from langcodes import Language
+
+from core.utils.requester import NonRetryableError, fetch_data
+
+
+logger = logging.getLogger(__name__)
+
+__all__ = [
+    "fetch_data",
+    "language_iso",
+    "NonRetryableError",
+    "_get_user",
+]
+
+
+def language_iso(code):
+    """Normalize a language code to its shortest ISO 639 form.
+
+    Uses the ``langcodes`` library to parse ``code`` and return the two-letter
+    language subtag when valid (e.g. ``"pt-BR"`` → ``"pt"``).
+
+    Returns an empty string when the code is ``None``, empty or cannot be
+    parsed into a valid language.
+    """
+    if not code:
+        return ""
+    try:
+        lang = Language.get(code)
+        if lang.is_valid():
+            return lang.language or ""
+    except ValueError:
+        pass
+    return ""
+
+
+def _get_user(request, username=None, user_id=None):
+    """Resolve the acting user from the current request context.
+
+    Attempts to look up the user by ``request.user_id`` first.  If that
+    attribute is missing (``AttributeError``), falls back to ``user_id``
+    or ``username``.
+
+    Returns ``None`` when no lookup parameter is available.
+    """
+    User = get_user_model()
+    try:
+        return User.objects.get(pk=request.user_id)
+    except AttributeError:
+        if user_id:
+            return User.objects.get(pk=user_id)
+        if username:
+            return User.objects.get(username=username)
diff --git a/requirements/base.txt b/requirements/base.txt
index 5c1bac1..ff491b9 100644
--- a/requirements/base.txt
+++ b/requirements/base.txt
@@ -42,3 +42,7 @@ git+https://git@github.com/scieloorg/packtools@4.12.6#egg=packtools
 # Langdetect
 # ------------------------------------------------------------------------------
 langdetect~=1.0.9
+
+# Langcodes
+# ------------------------------------------------------------------------------
+langcodes==3.5.1  # https://pypi.org/project/langcodes/